Unusual selective monitoring of N,N-dimethylformamide in a two-dimensional layered field-effect transistor

N,N-Dimethylformamide (DMF) is an essential solvent in industries and pharmaceutics. Its market size range was estimated to be 2 billion US dollars in 2022. Monitoring DMF in solution environments in real time is significant because of its toxicity. However, DMF is not a redox-active molecule; therefore, selective monitoring DMF in solutions in real time requires an unprecedented design at the scale of atomic resolution. In this paper, we propose a selective DMF sensor using a molybdenum disulfide (MoS2) field-effect transistor (FET). The sensor responds to DMF molecules, but not to similar molecules of formamide, N,N-diethylformamide, and N,N-dimethylacetamide. The plausible atomic mechanism is the oxygen substitution sites on MoS2, on which the DMF molecule shows exceptional orientation. The thin structure of MoS2-FET can be incorporated into a microfluidic chamber, which leads to DMF monitoring in real time by exchanging solutions subsequently. The designed device shows DMF monitoring in NaCl ionic solutions from 1 to 200 L/mL. This work proposes the concept of selectively monitoring redox-inactive molecules based on the non-ideal atomic affinity site on the surface of two-dimensional semiconductors.